This invention relates to a catheter whose structure enables sampling of blood by decreasing the potential for adherence of the catheter tip to a blood vessel wall or a blood clot.
Catheters are sterilized or sterilizable, hollow tubes that may be placed in a blood vessel to allow continual access to the blood without having to re-puncture the patient. Blood catheters are used to collect blood or administer medications over time. However, a recurring problem in catheters used to collect blood samples is that the catheter tip can become blocked when negative pressure is applied to draw blood. When blockage of the catheter occurs, the patient must be re-punctured to collect a new blood sample. The primary cause of blockage is adherence of the catheter tip to the sides of the vessel walls, thus preventing the return of blood flow. An additional cause of blockage is a blood clot that blocks the catheter tip.
An unfilled need exists for a catheter that decreases the chance of blockage when applying negative pressure during blood sampling.
U.S. Pat. No. 5,935,056 describes a device for viewing a region of a fallopian tube, comprising an optical viewing scope and an access catheter having a distal spacing structure which facilitates separation of the tubal wall of the fallopian tube from the optical viewing scope.
U.S. Pat. No. 5,531,673 describes a tubular ventricular catheter that prevents clogging, and reduces the tearing of brain tissue when the proximal tip of the device is withdrawn from the brain cavity. The catheter has a rounded open end and two longitudinal slots cut in the side wall of the proximal end. The longitudinal slots are scalloped by semi-circular cut-outs.
U.S. Pat. No. 5,509,910 describes a multi-part catheter which comprises a high strength bond between a tubular shaft and a more flexible distal tip by employing a high tensile strength transition segment.
U.S. Pat. No. 4,886,506 describes a catheter tube with improved torque control and a tapered end that allows a more secure connection to a soft tip.
U.S. Pat. No. 5,160,559 describes a guide catheter having a high strength, lap-joint tip bond, comprising two shaft members linked by a high surface area connection. The first shaft member is composed of a soft, deformable tubular tip, while the second shaft member is composed of a thermoplastic, tubular member.
U.S. Pat. No. 4,617,019 describes a method for cutting a catheter at an acute angle to reduce undesirable protuberances when the catheter is flattened for insertion.
U.S. Pat. No. 4,551,292 describes a process for fabricating a catheter having a soft, deformable, bulbous tip composed of a thermoplastic or elastomeric material.
U.S. Pat. No. 217,711 describes a urethra catheter with a xe2x80x9cduck-bill or V-shapedxe2x80x9d tip with elastic branches that compress to a wedge shape when the catheter enters and follows the canal of the urethra. Upon entering the bladder, the elastic branches of the V-shaped tip reopen to allow sampling of the bladder fluid.
None of these prior devices address the need for a catheter that reduces or eliminates blockage of a catheter when negative pressure is applied. An unfilled need exists for a catheter that avoids adherence to a blood vessel wall or to a blood clot.
I have discovered a catheter and a method that decreases the blockage problem while collecting blood. The device is a sterilized or sterilizable catheter with a non-planar tip. To avoid adherence to the blood vessel wall, the catheter tip is shaped, by either cutting or molding, in a way that makes the terminal end sufficiently non-planar to inhibit or prevent the formation of a seal with a blood vessel wall. The non-planar shape can, for example, be a V-shape tip whose branches are sufficiently short to maintain the catheter""s shape and to prevent closing by blood vessel wall pressure. In alternative embodiments, the non-planar tip can be serrated, castellated, or cut in an undulated manner. The tip should allow the passage of blood when the terminal end of the catheter is against a blood vessel wall, while maintaining sufficient strength to inhibit or prevent the expansion or collapse of the tip.